1. Field of the Invention
The invention relates to a coaxial plug-connector part according to the preamble of the independent claim. A coaxial plug-connector part of this kind is known, for example, from WO 2007/002692 A1.
2.Related Technology
FIG. 1 shows the longitudinal section through a coaxial plug connector as it is known in a similar design, for example, as an N-plug. It includes a plug part, generally designated 1 and a jack part, generally designated 2. The plug 1 includes an outer-conductor 3, within which, via a connecting washer 4, the internal conductor 5 is arranged in a coaxial manner. The coaxial line including the inner conductor 5 and the outer-conductor 3 continues at the rear of the plug 1, which is not illustrated in greater detail, for example, in a device or in a coaxial cable. On the outer-conductor 3, a cap nut 6, which is connected via a retaining ring 7 in an axial force-fit manner to the outer-conductor 3, is placed in a rotatable manner. The internal thread 8 of the cap nut 6 must be screwed onto the external thread 9 of the jack 2 in order to manufacture the coaxial connection, until the annular butting contact surface 10 of the outer-conductor 3 of the plug 1 contacts the corresponding annular butting contact surface 11 of the jack 2. In this context, the tip 12 of the internal conductor 5 is pushed into the radially-resilient sleeve-shaped bush 13 of the jack part 2.
The currently commercially-available coaxial plug connectors, as they are known by the references N-, 2.92 mm, SMA-, 1.85 mm-, 3.5 mm-, or 2.4 mm-plugs or respectively as so-called hermaphrodite connectors under the reference PC7, are all constructed according to this principle with a cap nut screwed onto the outer-conductor, wherein, in many cases, the cap nut can also be provided on the jack part.
The quality of a coaxial plug connector is quite substantially dependent upon a sufficiently-large axial pre-tensioning. Excessively small values can lead to an unreliable connection, because the low contact pressure on the outer-conductor is insufficient to guarantee a consistently-low transitional resistance over the entire periphery of the circular contact surface. As a result of the disturbed current distribution in the contact region of the outer-conductor, reflections and increases in attenuation can occur at relatively high frequencies: an effect which can hardly be determined in the low-frequency range, because there, a low transitional resistance even at a single contact point is sufficient for the entire connection.
Furthermore, an excessively-low axial pre-tensioning has the disadvantage that a plug connector can easily be loosened, especially by torque engagement with the screw-connected parts, without the cap nut coming into play. Conversely, an excessively-strong tightening can lead to premature wear of the plug and significant dimensional changes as a result of the mechanical stresses introduced. This applies in particular for parts with defined electrical length, such as short circuits in calibration kits.